Gas-powered impact hammer



May 5, 1970 R. J. DORN GAS-POWERED IMPACT HAMMER 4 Sheets-Sheet 1 FiledAug. 5, 1968 INVENTOR. Russell John Darn ATTORNEY May 5, 1970 R. J. DORNGAS-POWERED IMPACT HAMMER 4 Sheets-Sheet 2 Filed Aug. 5, 1968 wavy wm okp omb vfl QM V i INVENTOR. Russell John Dorn BY a 1. @w

ATTORNEY May 5, .1970 R. J. DORN GAS-POWERED IMPACT HAMMER 4Sheets-Sheet 5 Filed Aug. 5, 1968 INVENTOR. Russell John Dorn ATTORNE Yy 5, 1970 R. J. DORN 3,509,723

GAS-POWERED IMPACT HAMMER Filed Aug. 5, 1968 4 Sheets-Sheet 4 59 92 992O 8 5 y r50 g if g Q INVENTOR.

Russell John Dorn ATTORNEY 3,509,723 GAS-POWERED IMPACT HAMMER RussellJohn Dorn, Aurora, Colo., assignor to Arrow Manufacturing Company,Denver, Colo., a corporation of Colorado Filed Aug. 5, 1968, Ser. No.750,303 Int. Cl. F011) 31/00 C]. 60-57 9 Claims ABSTRACT OF THEDISCLOSURE A compressible-fluid-powered impact hammer is mounted on adirigible automotive vehicle. The hammer includes a cylindrical jacketslidably and telescopingly mounting a tool carrying impact ram. Aninternal plunger mounted within the jacket is received within an axialcavity in the inserted end of the ram to define an internal gas chamber.Hydraulic pressure fluid is used to retract the ram into the jacket andthereby compress the cowtained gas in the chamber. A valve mechanismreleases the hydraulic fluid pressure and the compressed gas expands todrive the ram to an impact point.

BACKGROUND OF THE INVENTION The present invention relates to acompressible-fluidpowered impact hammer mechanism. More particularly,the invention resides in a nitrogen gas-powered impact hammer findingparticular, but not necessarily exclusive, use as a vehicle mountedpercussion tool for the tamping of fills, the cutting and breaking ofpavements, the driving of posts and pilings, the demolition ofstructures and like operations.

The use of a compressed gas to power an impact hammer, is an old andWell known expedient. Difliculties have been encountered, however, inobtaining satisfactory sliding seals, and in providing efiicient meansfor retracting the ram to load or cock the hammer. Additional problemshave also been encountered in connection with throttling of the pressurefluid utilized to compress the gas when the ram is actuated or fired.The throttling action results in a substantial heat rise and degradationof the pressure fluid, as well as in a loss of efi'iciency in that thecompressed gas must not only drive the ram, but must also act againstthe pressure created by throttling the fluid.

OBJECTS OF THE INVENTION The principal object of the present inventionis to provide a novel gas-powered impact hammer which is rugged inconstruction, susceptible of severe use in a wide variety ofconstruction and demolition operations, is simple in operation, requiresa minimum of maintenance, and is suitable for mounting on a dirigibleautomotive vehicle.

Another object of the present invention is to provide an efiicientpowerful gas-powered impact hammer in which the ram is retracted and thegas is compressed by means of an improved hydraulic fluid circuit and inwhich throttling of the fluid is minimized and the hydraulic fluidpressure can be quickly reduced to eliminate back pressure as the ram isdriven by the expanding gas.

SUMMARY The foregoing objects are accomplished by a vehicle mounted,pressure-fiuid-controlled-gas-powered impact hammer as described herein.The vehicle includes a wheeled chassis with a frame rotatably mountedthereon and carrying the power elements and an angular boom. The hammeris mounted on the end of the boom and is positioned by hydraulic meanscontrolled by an operator at the control station on the vehicle. Thehammer embody- United States Patent O 3,509,723 Patented May 5, 1970 iceing the invention is made up of a ram slidably mounted in a jacket. Theinner end of the ram is tubular and receives a fixed compressor rod. Agas chamber is defined between the tubular end of the ram and thecompressor rod in which gas is compressed to act as motive power for theram. Substantially coextensive annular chambers are defined within thejacket. The ram is received in one of the annular chambers while theother acts as an annular exhaust passage. The hammer is controlled by apressure fluid operated solenoid valve mechanism which in turn actuatesa spool valve which controls the operation of the ram. This isaccomplished by the selective opening or closing of the portscommunicating between the pressure side and the exhaust side of the ram.The ram is cocked or loaded by means of pressure fluid which actsagainst the ram to retract it and compress the gas. To fire the ram thefluid pressure is reduced to zero by shifting the solenoid 'valve. toopen both annular chambers to exhaust.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a vehiclemounting an impact hammer embodying the present invention.

FIG. 2 is a longitudinal, detailed, section view of an impact hammerembodying the present invention with the impact ram retracted.

FIG. 3 is an enlarged, fragmentary, section view showing one end portionof the hammer shown in FIG. 2, and illustrating particularly theservo-valve control mechanism.

FIG. 4 is a section view taken substantially in the plane of line 4-4 onFIG. 3.

FIG. 5 is a section view taken substantially in the plane of line 5-5 onFIG. 3.

FIG. 6 is a section view, similar to that shown in FIG. 2, but in agenerally schematic form.

FIG. 7 is a schematic view similar to FIG. 6, but showing the ram in apartially extended position.

FIG. 8 is a schematic view similar to FIG. 6, but showing the ram in afully extended position.

FIG. 9 is a schematic view similar to FIG. 6, but showing the ram in apartially retracted position.

DESCRIPTION OF THE PREFERRED EMBODIMENT In general There is shown in thedrawings, with particular reference to FIG. 1, a pressure fluidcontrolled, gas powered impact hammer, indicated generally at 20',mounted at the outboard end of a boom, indicated generally at 21,carried on a dirigible, wheeled, automotive vehicle, indicated generallyat 22. The vehicle may be either a conventional piece of roadworkingequipment, or may be a specially constructed unit for carrying the boom21 and hammer 20. For purposes of illustration, the vehicle shown inFIG. 1 comprises a chassis 24 provided, in the present instance, withwheels 25, although crawler tracks may be utilized to advantage for someapplications. The wheels 25 are individually mounted and journaled onthe chassis 24, and are each powered by a pressure fluid driven motor(not shown). Appropriate steering gear and linkage (not shown), alsopressure fluid powered, are provided as is conventional in the art.

For carrying and mounting the various components of the assembly,including a power source 28, operator and control stations, and the boom21, a frame 26 is supported on the chassis by a rotatable mountingstructure 27, so that the frame 26 may be swungor rotated about avertical axis. The frame 26 carries an internal combustion engine drivenpower unit 28 which includes a pressure fluid or hydraulic pump forsupplying pressure fluid to the various components of the vehicle, boomand hammer. For controlling the vehicle and its adjuncts, an operatorcontrol station, including a seat 29, steering gear 30 and controls 31,is mounted on the frame 26. The vehicle is driven and all controls areactuated from the operators station 29. The unit is thus suitable forone man operation and is a completely self-contained, self-poweredapparatus. Hydraulic fluid is supplied to the various components throughappropriate conduit and the rotatable mounting structure 27 includesmeans making provision for the application of pressure fluid from thepower source 28 to the various hydraulic motors carried on the chassis24 for driving the wheels 25 and steering mechanism.

For carrying the impact hammer 20 embodying the present invention, agenerally angular boom 21 is mounted on the frame 26 for swingingmovement in a generally vertical plane, so that the position of thehammer may be raised or lowered. The boom can be moved up and down in avertical plane and, by rotating the frame 26 about a vertical axis withrespect to the chassis, the boom can be swung from side to side, therebyenabling the operator to position it throughout a complete 360 arearelative to the chassis. For raising the boom 21, a hydraulic ram 35 isfixed between the frame 26 and the boom at approximately the apex of theangle therein. This hydraulic ram 35 is actuated by controls located atthe control station 31, and receives its pressure fluid from the powerunit 28 on the vehicle.

As shown in FIG. 1, the hammer 20 is mounted on the outer end of theboom 21. The necessary hydraulic fluid conduits for operating the hammerand for positioning the same are secured on and carried by the boom. Inorder to support the hammer on the boom, a yoke 38 is pivotally mountedon the outer end of the boom. To this end, the boom is formed with apair of outwardly directed cars 39 carrying a pin 40 journaled betweenthem for rotation about a horizontal axis. The yoke 38 is carried on thepin 40 intermediate the cars 39. For rotating the pin and therebyswinging the yoke in a vertical plane, a lever 41 is afiixed to one endof the pin 40 outwardly of the adjacent boom ear 39. The free end of thelever is secured to a hydraulic ram 42 mounted on the boom 21. Actuationof the ram thus serves to rotate the pin about a horizontal axis therebyto swing the yoke and the structures mounted thereon in a verticalplane. The yoke in turn mounts a cylinder (not shown) for receiving atrunnion (not shown) to which is secured a hammer mounting bracket andshock absorber 45. Hydraulically actuated rams 46 are mounted on theyoke 38 for rotating the trunnion thereby to swing the mountingstructure and the hammer 20 carried thereby about a generally horizontalaxis so that the hammer 20 can be swung from side to side.

Pressure-fluid controlled gas-powered impact hammer The impact hammer 20embodying the present invention is illustrated in detail in thedrawings, and particularly in FIGS. 2 and 3, and comprises an outercylindrical jacket '50 having a bore 51 in which is telescopingly andslidingly received an impact ram 52. A tool or guide mounting flange 54is provided on the lower end of the jacket 50, and the impact end 55 ofthe ram 51 is shaped to receive a hammer tool or like instrument 53. Atthe lower or impact end of the jacket from which the ram projects, thejacket cylinder is recessed to define a counter bore 56 in which ismounted cylindrical bearing-supporting inner and outer inserts 58, 59,one of which inserts 58 includes an internally tapered bore 60 extendingpart way through the insert and tapering from a larger diameter at itsinnermost end 61 to a relatively smaller diameter. The insert 58 seatsagainst a shoulder 62 defined in the jacket 50 by the counter bore '56.At its end opposite from the tapered bore, the insert 58 is providedwith a bore 64 in which is mounted a ram guiding and supporting bearingring 65, the inner surface of which is provided with seals 66. The outerinsert 59 is positioned in the jacket bore 56 and seats against theinner insert 58 and a shoulder '68 defined by a counter bore 69 in theoutermost end of the jacket 50. The insert 59 supports a bearing ring 70which is provided with a dust seal 71 adapted to engage the surface ofthe ram 52.

For supplying pressure fluid to the interior of the jacket, a pressurefluid input port 74 is provided in the jacket 50. This port '74communicates with an input channel 75 in the insert 58 and a pluralityof input passages 76 therethrough opening into the tapered bore 60surrounding the ram 52. Pressure fluid is supplied from a pressure fluidsource on the vehicle through appropriate conduits (not shown) securedto the boom 21. A check valve (not shown) may be provided in thepressure fluid input line so that unidirectional flow is achieved.

The inner end portion 78 of the ram 52 is telescoped within the jacket50, and is generally tubular to define a gas receiving cavity 79. Forsupplying a compressible gas to the cavity, the ram is provided,adjacent its impact or tool end 55, with a fill bore or passage 87, anda gas valve fill stem 81. To support the inner end 78 of the ram 50 forsliding movement, the jacket is provided, at its end opposite from themounting flange 54, with an end member 80 seated in the jacket andsupported against an internal shoulder 82 defined by a counter bore 83within the end of the jacket. An end cap 84, threadably and sealinglyengaged within the jacket 50, securely holds the end member 80 withinthe jacket and against the seat 82. The end member 80 is provided at oneend with a central axially extending valve spool recess 85, and at itsother end the member 80 supports a plunger or compressor rod 86 whichextends axially within the jacket 50 and is telescopingly receivedwithin the tubular end 78 of the ram 52. The end member 80 also supportsan internal cylinder or sleeve 88 co-extensively surrounding the plungeror compressor rod 86 and positioned in the space defined between theouter surface of the rod 86 and the inner surface 51 of the jacket 50.The inner surface 89 of the cylinder or sleeve 88 defines, with theouter surface of the plunger or compressor rod 86, a first annularchamber 90 within which the tubular end 78 of the ram 52 is received.The outer surface 91 of the cylinder or sleeve 88 defines, with theinner surface 51 of the jacket '50, a second annular chamber 92, whichis generally co-extensive with the first annular chamber 90. To furtherdefine a compressible-gas chamber, the free end of the compressor rod 86embodies a generally axial recess or chamber 94.

The tubular end of the ram is enlarged to define an internal shoulder'95, and at its free end mounts an annular bearing member 96 whichcarries appropriate seals 98, 99 for engaging the walls of the internalsleeve 88 and the compressor rod 86 respectively. With the foregoingsleeve and seal arrangement, it can be observed that the gas chamberdefined by the chambers 79 and 94 is completely sealed so that, whencharged with a compressible gas, the gas may either be compressed orallowed to expand without substantial leakage. The valve stem 81 is, ofcourse, provided for use in replenishing the gas supply to make up forthe small amount of leakage which will inevitably occur.

The first annular chamber 90 defined between the compressor rod 86 andthe sleeve 88, is generally considered to be an exhaust chamber, andpassages or ports 100 are provided connecting this chamber with thevalve recess 85. The recess 85 further communicates, through appropriatepassages 101, with an exhaust port 102 and associated pressure fluidconduit (not shown) which leads to a pressure fluid supply or sump onthe vehicle. Again, a one way check valve may be provided in the exhaustline so that fluid flow through the exhaust port is unidirectional.

The second annular chamber 92 defined between the sleeve 88 and thejacket 50 communicates with the first annular chamber 90 throughradially extending passages 104 in the end member 80. For purposes ofselectively opening or closing these passages to control thecommunication between the first and second annular chambers, there isprovided a sliding valve spool 105 mounted in the recess 85 in the endmember 80. The spool 105 is provided with generally axially extendingpassages 106 to insure open communication between the exhaust port 102,the end member passages 100, and the first annular chamber 90. The spool105 is selectively positioned by a servo valve stem 108 which is securedto the spool 105 and extends outwardly through the end cap 84 where itis engaged with a servo valve control mechanism 109. The servo valvemechanism 109 includes a cylinder 110 surrounding a piston 111 aflixedto the servo valve stem 108. Pressure fluid ports 112, 113 are providedfor applying pressure fluid from the pressure fluid source on thevehicle to a selected side of the piston 111. Appropriate seals andsealing rings are provided as is conventional practice in the art.Further, a bushing 114 is desirably provided in the recess 85 in the endmember 80 for slidably receiving the valve spool 105.

Operation of the impact ram In the operation of the impact ram 20 hereindescribed, the operator of the ram carrying vehicle 22 positions the ram20 with the impact tool 53 operatively adjacent a work surface. Thesolenoid operated servo control valve 109 is actuated, by applyingpressure fluid to port 112, to position the valve spool 105 to close theradial passages 104 communicating between the end member recess 85 andthe second or outer annular chamber 92 in the jacket 50. Referring toFIG. 6, the valve spool 105 is moved to the right by the application ofpressure fluid to solenoid valve port 112. It will be observed that thefirst or inner annular chamber 90 containing the telescoping tubular end78 of the ram 52 is at all times open to the pressure fluid exhaust linethrough port 102, the axial passages 100 in the end member 80 and theaxial passages 106 in the valve spool 105. Thus the inner annularchamber 90 is effectively at zero pressure. Pressure fluid is thensupplied to the pressure fluid port 74 in the jacket 50 by the actuationof appropriate controls at the operator controlled station 31. Becausethe second or outer annular chamber 92 is closed to exhaust by the valvespool 105, fluid pressure will build up in the annular chamber. Thediflerential across the inserted end 78 of the ram 52 results in a forcebeing exerted on shoulder 95 on the ram. This force moves the raminwardly of the jacket, as shown in FIG. 9, and effects a telescopingmovement between the ram and the compressor rod or plunger 86. In thismanner, the contained gas in chamber 79 is compressed to a pressuresubstantially equal to that of the pressure fluid. For example,hydraulic oil pressure at 2000 lbs. per square inch in the constructionshown, will compress the nitrogen gas confined within the gas chamber 79to a pressure of 2000 lbs. per square inch. As the ram is withdrawn intothe jacket to the position shown in FIG. 6, the pressure fluid fillingthe first annular space behind the ram will be exhausted through theexhaust port 102 to the supply source of the pressure fluid. This fluidflows from the inner annular chamber 90 through the generally axialpassages 100 in the end member 80, thence through the axially directedpasages 106 in the spool 105 and out through the radial passages 101 inthe end member 80 to the exhaust port 102. When the ram has been fullyretracted within the jacket, as shown in FIG. 6, the containedcompressed nitrogen gas in chambers 79*, 94 is at maximum pressure andthe ram is cocked ready for hammer operation. A check valve in the fluidpressure supply line prevents pressure fluid from flowing out of theinlet port 74 so that the ram remains in a fully cocked or loadedposition until it is fired.

To fire the ram to achieve a hammer blow of the tool 53 on a worksurface, the servo valve 109 is reversed to withdraw the valve spool105, a left hand direction as shown in FIG. 7, and open the radial ports104. Communication is thereby opened between the two annular chambersand 92 through the axial ports 100 in the end member 80. Because theannular chambers 90 and 92 are also open to the exhaust port 102 and arethus effectively at zero pressure, the force on the loading shoulder isreduced to substantially zero. There being no pressure fluid restrainton the ram 52, the confined compressed nitrogen gas rapidly expands anddrives the ram outwardly of the jacket as shown in FIG. 7, to an impactposition. Pressure fluid contained in the first annular chamber 90between the inner sleeve 88 and the plunger or compressor rod 86 flowsthrough the outer annular chamber 92 and the radial ports 104 into theend member recess 85. The pressure fluid will then be drawn into chamber90 in back of the tubular end of the ram 78 as the ram moves out ofchamber 90, that is, toward the right as shown in FIG. 7. Because ofthis flow of fluid into the inner chamber 90, it will be appreciatedthat there is little or no throttling effect and the hydraulic fluidremains at essentially zero pressure or even under a slight vacuum.

As the ram approaches its outer limit of travel, as shown in FIG. 8, theshoulder 95 on the end 78 of the ram is received in the tapered bore 60of the sleeve insert 58 which is mounted within the end of the jacket50. This has the effect of gradually compressing pressure fluid in thespace defined between the outer surface of the ram, the inner surface ofthe bore in the insert 58, and the shoulder 95. Inasmuch as the bore 60of the insert 58 is tapered, the pressure increases rapidly as the rammoves forward. In

this manner, fluid trapped in the insert bore acts as a cushion andretarding element to slow and stop the movement of the ram before theshoulder 95 comes into contact with the end of the insert 59. Under mostcircumstances however, the tool will impact against a work surface priorto or just as the shoulder 95 enters the tapered bore 60. The shock ofthe impact is transmitted through the ram and jacket to the shockabsorber mounting 45 on the end of the boom 21. This mounting absorbsthe shock and vibration from the impact so that severe stresses are nottransmitted through the boom to the vehicle.

The hammer mechanism described above is position independent and willoperate equally well in any position, whether vertical, horizontal orany position in between. The hammer may be directed upwardly, sidewiseor downwardly thereby making the unit admirably suited not only for roadwork but for building demolition, mine work and the like.

I claim as my invention:

1. A gas powered impact ram comprising, in combination, a jacket, a ramslidably and telescopingly mounted in said jacket, said ram having animpact end extending outwardly from said jacket and a tubular endinserted within said jacket, a compressor rod fixedly mounted in saidjacket and telescopingly received within the tubular end of said ram,said compressor rod and tubular end of said ram defining a gas chamber,a compressible gas contained within said chamber, pressure fluid meansfor retracting said ram into said jacket thereby to compress thecompressible gas between said ram and said rod, and means for releasingsaid pressure fluid retracting means, whereby said compressed gas drivessaid ram with impact force outwardly of said jacket.

2. A pressure fluid controlled, gas powered impact hammer comprising, incombination, a generally cylindrical jacket, a compressor rod fixedlymounted on said jacket at one end thereof and extending axially withinthe jacket, an internal sleeve mounted on said jacket and extendingaxially into said jacket in substantially coextensively surroundingrelation with said compressor rod, said sleeve defining with said rod afirst internal annular chamber and defining with said jacket a secondinternal annular chamber, means for controlling the flow of pressurefluid between said annular chambers, means defining a pressure fluidexhaust passage through said jacket, in open communication with saidfirst annular chamber, a ram slidably mounted in telescoping relation insaid jacket, said ram having an impact end extending outwardly of saidjacket and a tubular end inserted into the first annular space andtelescopingly receiving said compressor rod, to define therewith achamber internally of said ram for confining a charge of gas, saidtubular end of the ram defining an annular shoulder adjacent theinnermost end thereof, sealing means on said tubular end slidablyengaging the opposed walls of said first annular chamber, means defininga pressure fluid port opening through the jacket adjacent the impact endof the ram and communicating with said first and second annularchambers, means slidably and sealingly supporting the impact end of saidram with said jacket, and servo valve control means on said jacket forselectively actuating said controlling means to obstruct the flow ofpressure fluid between said annular chambers so that the application offluid pressure within said annular chambers exerts a retracting force onsaid shoulder to telescope the ram inwardly of the jacket and thereby tocompress said charge of gas contained in the chamber defined betweensaid compressor rod and said impact ram, and for selectively actuatingsaid controlling means to release the flow of pressure fluid betweensaid annular chambers so that pressure fiuid contained in said secondannular chamber is released to flow to said first annular chamber and tosaid exhaust port whereby the retracting force on said ram is releasedso that said compressed gas rapidly expands to drive said ram forciblyoutwardly of the jacket.

3. A pressure fluid controlled, gas powered impact hammer comprising, incombination, a generally cylindrical jacket, internal bearing meansmounted in said jacket adjacent one end thereof, an end member mountedin said jacket adjacent the other end thereof, a compressor rod fixedlymounted on said end member and extending axially within the jacket, aninternal sleeve mounted on said end member and extending axially intosaid jacket in substantially coextensively surrounding relation withsaid compressor rod, said sleeve defining with said rod a first internalannular chamber and defining with said jacket a second internal annularchamber, said end member having an axially extending recess definedtherein, means defining generally axially extending passages throughsaid end member opening into said recess and said first annular chamber,means defining generally radially extending passages through said endmember opening into said recess and said second annular chamber, meansdefining a pressure fluid exhaust passage through said end member andjacket, a valve spool slidably mounted in said recess for selectivelyopening and closing said radial passages, said spool having passagesextending in an axial direction therethrough and providing opencommunication between said axial passages in said end member and saidpressure fluid exhaust port, servo control means mounted on said jacketfor selectively positioning said spool for opening or closing saidradial passages, a ram slidably mounted in telescoping relation in saidjacket, said ram having an impact end extending outwardly of said jacketand a tubular end inserted into the first annular space andtelescopingly receiving said compressor rod, said compressor rod havinga recess defined in the free end thereof for confining a charge of gaswithin said tubular end of the ram, said tubular end of the ram definingan annular shoulder adjacent the innermost end thereof, sealing means onsaid tubular end slidably engaging the opposed walls of said firstannular chamber, means defining a pressure fiuid port opening throughthe jacket adjacent the impact end of the ram and communicating withsaid first and second annular chambers, the impact end of said ram beingslidably and sealingly supported by said internal bearing means, andservo valve control means on said jacket for positioning said valvespool to close said radial passages, so that the application of fluidpressure within said annular chambers exerts a retracting force on saidshoulder to telescope the ram inwardly of the jacket and thereby tocompress said charge of gas contained in the chamber defined betweensaid compressor rod and said impact ram, and for positioning said valvespool to open said radial passages so that pressure fluid contained insaid second annular chamber is released to flow to said first annularchamber and to said exhaust port thereby releasing the retracting forceon said ram so that said compressed gas rapidly expands to drive saidram forcibly outwardly of the jacket.

4. A gas powered impact ram as defined in claim 1 including means withinsaid jacket for retarding movement of said ram and stopping the same atthe outer limit of travel thereof.

5. A gas'powered impact ram as defined in claim 2 including a secondinternal sleeve coaxially mounted within said jacket axially spacedlyadjacent said compressor rod, said sleeve having a bore therein taperedfrom a larger diameter at its end adjacent said compressor rod to asmaller diameter at its opposite end, said sleeve being adapted toclosely receive said annular shoulder on said ram in progressively moreconfining releationship Whereby as said shoulder enters said taperedbore pressure fluid is confined and compressed between said shoulder andsaid tapered bore to retard the movement of said ram and stop the sameat the outer limit of travel thereof.

6. A gas powered impact ram as defined in claim 2 wherein said meansslidably and sealingly supporting the impact end of said ram within saidjacket comprise a bearing support sleeve mounted within said jacket incoaxial surrounding relation with said ram and a pair of spaced apartbearing members supported Within said sleeve for sealingly and slidinglysupporting said ram.

7. A gas powered impact ram as defined in claim 3 wherein said endmember comprises a generally cupshaped member, said compressor rod beingfixedly mounted on the base of said cup-shaped member, and a peripheralshoulder defined on said cup-shaped member adapted to seat against aninternal shoulder defined in a the inner wall of said jacket.

8. A gas powered impact ram as defined in claim 7 including an end capthreadably engaged within said jacket for holding said cup-shaped membertherein, said end cap mounting said servo valve control means and havingan axially extending aperture therethrough for receiving said valvestem.

9. A gas powered impact ram as defined in claim 7 wherein saidcup-shaped member includes an internal sleeve bushing slidablysupporting said valve spool.

References Cited UNITED STATES PATENTS 2,731,892 1/1956 Simmonds.2,787,123 4/1957 Delvaux 6057 2,827,764 3/ 1958 Simmonds 605 1 FOREIGNPATENTS 485,617 5/ 193 8 Great Britain. 729,941 5/ 1955 Great Britain.

EDGAR W. GEOGHEGAN, Primary Examiner US. Cl. X.R.

